Multilayer scale growth

Fig. 7.3 Simplified scheme for the diffusion-controlled growth of multilayered scales on pure iron and mild steel above 570° C...

The latter can develop into a multilayered scale during the long-term oxidation above 1000°C [181]. Growth of such rutile scales was based on the simultaneous diffusion of titanium and oxygen ions through the oxide layer in opposite directions. 

The process described so far occurs repeatedly and, after longer testing times or at higher temperatures, multilayered scales are formed, as shown in Fig. 2-40, which offer only limited protection. Scale growth kinetics resulting from this situation can often be approximated by quasi-linear behavior (Fig. 

Figure 5.24 Oscillogram of a current transient at multinuclear multilayer growth in the standard system Ag (100)/AgNO3 15.45). Overvoltage / = - 14 mV current scale 2 (tA div" time scale 5 ms divV...

The development of film growth processes for large scale multilayer HTS device technologies is crucially dependent not only upon the ability to fabricate large area HTS metal oxide films, but also on the ability to reliably grow HTS lattice-matched, CTE-matched, chemically compatible, low E/tan d metal oxides for use as dielectrics, buffers, substrates, interlayers, and overlayers [282]. (See Fig. 2-11 for an illustration of a complex HTS device). MOCVD processes appear to offer advantages that could be employed to this end, provided that reliable routes to dielectric films can be established. Films of many of the aforementioned lattice-matched metal oxide substrate and/or interlayer materials (Table 2-3) have been grown by MOCVD (see below). 

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